To do this you need the IP address of your Pi on your local network. You can get that with
ifconfig on the command line. Let's say, for example, that it was 192.168.1.42.
Then you want to forward port 22 from your router to your Pi. (Port 22 is the standard port for
ssh.) In the input form that you have, it looks like that will require a row that looks like this:
22, 22, 192.168.1.42, 22, 22, TCP`
Then probably you need to click "Enable".
You'll also need to know the public IP address at your house to make the connection from work. You can get that if you Google for "ip address". They will display your public IP address at the top of the results page. Let's say, for example, that you got 220.127.116.11.
Now you can connect by
ssh to your public IP address to connect to your Pi. From Linux that would be
Using the (notional) IP addresses in the text above. You need to modify that to your actual public IP address.
Before doing this, however, note the following:
Anyone else can also
ssh to your Pi using your public IP address. You'll need to take care with security. You will be scanned by bots that try to log into port 22 using common passwords and other exploits. Right now your router's firewall is blocking that out for you.
If someone penetrates your home network because you enabled port forwarding and made a security mistake, they will likely be able to take control of other computers and devices on your home network.